1// SPDX-License-Identifier: GPL-2.0-only
 2/*
 3 * Copyright (C) 2020 Western Digital Corporation or its affiliates.
 4 * Adapted from arch/arm64/kernel/efi.c
 5 */
 6
 7#include <linux/efi.h>
 8#include <linux/init.h>
 9
10#include <asm/efi.h>
11#include <asm/pgtable.h>
12#include <asm/pgtable-bits.h>
13
14/*
15 * Only regions of type EFI_RUNTIME_SERVICES_CODE need to be
16 * executable, everything else can be mapped with the XN bits
17 * set. Also take the new (optional) RO/XP bits into account.
18 */
19static __init pgprot_t efimem_to_pgprot_map(efi_memory_desc_t *md)
20{
21	u64 attr = md->attribute;
22	u32 type = md->type;
23
24	if (type == EFI_MEMORY_MAPPED_IO)
25		return PAGE_KERNEL;
26
27	/* R-- */
28	if ((attr & (EFI_MEMORY_XP | EFI_MEMORY_RO)) ==
29	    (EFI_MEMORY_XP | EFI_MEMORY_RO))
30		return PAGE_KERNEL_READ;
31
32	/* R-X */
33	if (attr & EFI_MEMORY_RO)
34		return PAGE_KERNEL_READ_EXEC;
35
36	/* RW- */
37	if (((attr & (EFI_MEMORY_RP | EFI_MEMORY_WP | EFI_MEMORY_XP)) ==
38	     EFI_MEMORY_XP) ||
39	    type != EFI_RUNTIME_SERVICES_CODE)
40		return PAGE_KERNEL;
41
42	/* RWX */
43	return PAGE_KERNEL_EXEC;
44}
45
46int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
47{
48	pgprot_t prot = __pgprot(pgprot_val(efimem_to_pgprot_map(md)) &
49				~(_PAGE_GLOBAL));
50	int i;
51
52	/* RISC-V maps one page at a time */
53	for (i = 0; i < md->num_pages; i++)
54		create_pgd_mapping(mm->pgd, md->virt_addr + i * PAGE_SIZE,
55				   md->phys_addr + i * PAGE_SIZE,
56				   PAGE_SIZE, prot);
57	return 0;
58}
59
60static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data)
61{
62	efi_memory_desc_t *md = data;
63	pte_t pte = ptep_get(ptep);
64	unsigned long val;
65
66	if (md->attribute & EFI_MEMORY_RO) {
67		val = pte_val(pte) & ~_PAGE_WRITE;
68		val |= _PAGE_READ;
69		pte = __pte(val);
70	}
71	if (md->attribute & EFI_MEMORY_XP) {
72		val = pte_val(pte) & ~_PAGE_EXEC;
73		pte = __pte(val);
74	}
75	set_pte(ptep, pte);
76
77	return 0;
78}
79
80int __init efi_set_mapping_permissions(struct mm_struct *mm,
81				       efi_memory_desc_t *md,
82				       bool ignored)
83{
84	BUG_ON(md->type != EFI_RUNTIME_SERVICES_CODE &&
85	       md->type != EFI_RUNTIME_SERVICES_DATA);
86
87	/*
88	 * Calling apply_to_page_range() is only safe on regions that are
89	 * guaranteed to be mapped down to pages. Since we are only called
90	 * for regions that have been mapped using efi_create_mapping() above
91	 * (and this is checked by the generic Memory Attributes table parsing
92	 * routines), there is no need to check that again here.
93	 */
94	return apply_to_page_range(mm, md->virt_addr,
95				   md->num_pages << EFI_PAGE_SHIFT,
96				   set_permissions, md);
97}